The development of new and more energy efficient illumination devices is one of the important technical challenges which society faces. Common technologies which are more energy efficient than traditional lighting solutions are often based on solid state light sources such as Light Emitting Diodes (LEDs).
Most, if not all, commercially available solid state light sources having a high efficiency emit light also of undesired wavelengths e.g. UV, blue, violet etc. Further, the light emitted from solid state light sources is not focused. High intensity light sources are interesting for many applications including spot lighting, digital light projection, vehicle lighting, lamps and luminaires. For these purposes it is possible to use wavelength converters which convert light of a shorter wavelength, into light of a longer wavelength in a highly transparent luminescent material. In order to increase brightness or the intensity of the light emitted, light of a longer wavelength can then be extracted from just one surface of a wavelength converter.
However, in such applications it is important to effectively couple the light from a light source into the wavelength converter which often comprises transparent phosphor for providing wavelength conversion. Furthermore, it is desirable to maintain the generated light within the luminescent layer to avoid light loss from the points where LEDs are optically coupled to the luminescent layer. U.S. Pat. No. 7,982,229 describes a conversion structure comprising phosphor which receives light from blue LEDs, converts the light into longer wavelength light and guides it to an exit surface, where the resulting brightness can be high. However, such a lighting device does not allow a customer to customize or adapt the lighting device in any way to take into account specific desirable characteristics of the lighting device such as color, shape or aspect ratio. Further, new developments may provide more efficient wavelength converters which should desirably be used in such lighting devices. US2009/0086475A1 discloses a color tunable light emitting device in which a phosphor component, which has a varying thickness, can be moved relative to a light source. EP2555261A1 discloses a phosphor element comprising portions with different phosphors and in which this element can be moved with respect to a light emitting area.